Data from: Sexual selection on spontaneous mutations strengthens the between-sex genetic correlation for fitness

A proposed benefit to sexual selection is that it promotes purging of deleterious mutations from populations. For this benefit to be realised, sexual selection, which is usually stronger on males, must purge mutations deleterious to both sexes. Here, we experimentally test the hypothesis that sexual selection on males purges deleterious mutations that affect both male and female fitness. We measured male and female fitness in two panels of spontaneous mutation-accumulation lines of the fly, Drosophila serrata, each established from a common ancestor. One panel of mutation accumulation lines limited both natural and sexual selection (LS lines), whereas the other panel limited natural selection, but allowed sexual selection to operate (SS lines). Although mutation accumulation caused a significant reduction in male and female fitness in both the LS and SS lines, sexual selection had no detectable effect on the extent of the fitness reduction. Similarly, despite evidence of mutational variance for fitness in males and females of both treatments, sexual selection had no significant impact on the amount of mutational genetic variance for fitness. However, sexual selection did reshape the between-sex correlation for fitness: significantly strengthening it in the SS lines. After 25 generations, the between-sex correlation for fitness was positive but considerably less than one in the LS lines, suggesting that, although most mutations had sexually concordant fitness effects, sex-limited and/or sex-biased mutations contributed substantially to the mutational variance. In the SS lines this correlation was strong and could not be distinguished from unity. Individual-based simulations that mimick the experimental setup reveal two conditions that may drive our results: (1) a modest-to-large fraction of mutations have sex-limited (or highly sex-biased) fitness effects, and (2) the average fitness effect of sex-limited mutations is larger than the average fitness effect of mutations that affect both sexes similarly.性选择（sexual selection）的一项潜在益处是，它可促进种群清除有害突变（deleterious mutations）。要实现这一益处，通常对雄性作用更强的性选择，必须能够清除对两性均有害的突变。在此，我们通过实验检验了如下假说：对雄性施加的性选择，能够清除同时影响雄性与雌性适合度（fitness）的有害突变。 我们以两批均由同一共同祖先种群建立的塞拉塔果蝇（Drosophila serrata）自发突变积累品系（spontaneous mutation-accumulation lines）为实验材料，测定了两性的适合度。其中一批突变积累品系同时限制了自然选择（natural selection）与性选择（以下简称LS品系），另一批则仅限制自然选择，允许性选择发挥作用（以下简称SS品系）。 尽管突变积累导致LS与SS品系的雌雄适合度均出现显著下降，但性选择对适合度下降的幅度未产生可检测到的影响。 类似地，尽管两种处理组的雌雄果蝇均存在适合度相关的突变遗传变异方差，但性选择对适合度相关的突变遗传变异量未产生显著作用。 不过，性选择确实重塑了适合度的两性间相关系数：在SS品系中，该相关系数得到了显著增强。经过25代繁育后，LS品系的适合度两性间相关系数为正值，但显著小于1，这表明尽管多数突变的适合度效应具有两性一致性，但性别限制性突变和/或性别偏倚突变仍对突变遗传方差做出了显著贡献。而在SS品系中，该相关系数极强，与1无显著差异。 模拟本实验设计的个体水平模拟实验（individual-based simulations）揭示了可解释本研究结果的两个条件：(1) 有中等至大量比例的突变存在性别限制性（或高度性别偏倚）的适合度效应；(2) 性别限制性突变的平均适合度效应，强于对两性适合度影响相近的突变的平均适合度效应。